The present invention provides novel polycarbonate modified vinyl esters, as well as cured compositions prepared from said vinyl esters.
Vinyl esters are the reaction product of about equivalent amounts of a monounsaturated monocarboxylic acid and a polyepoxide. One class of vinyl esters is described in U.S. Pat. No. 3,367,992 where dicarboxylic acid half esters of hydroxyalkyl acrylates or methacrylates are reacted with polyepoxide resins. Bowen in U.S. Pat. Nos. 3,066,112 and 3,179,623 describes the preparation of vinyl esters from monocarboxylic acids such as acrylic and methacrylic acid. Bowen also describes alternate methods of preparation wherein a glycidyl methacrylate or acrylate is reacted with the sodium salt of a dihydric phenol such as bisphenol A. Vinyl esters based on epoxy novolac resins are described in U.S. Pat. No. 3,301,743 to Fekete et al. Fekete et al describe vinyl esters where the molecular weight of the polyepoxide is increased by reacting a dicarboxylic acid with the polyepoxide resin as well as acrylic acid, etc. in U.S. Pat. No. 3,256,226. Other difunctional compounds containing a group which is reactive with an epoxide group, may be utilized in place of the dicarboxylic acid. All of the above-described resins, which contain the characteristic linkages ##STR1## terminal polymerizable vinylidene groups are classified as vinyl esters.
The vinyl ester is typically combined with a reactive diluent, a copolymerizable vinyl monomer, to alter the viscosity of the mixture, to vary the properties of the cured coating, or for other known reasons. Most any vinyl monomer may be employed which is copolymerizable with the unsaturated groups of the vinyl ester. Such monomers include both monovinyl and polyvinyl monomers. Typical monomers include the alkenyl aromatic monomers such as styrene, .alpha.-methylstyrene, vinyltoluenes, t-butylstyrenes, and the like; and alkyl and hydroxyalkyl esters of acrylic and methacrylic acid such as methyl, ethyl, propyl, butyl, cyclohexyl and hydroxyethyl, hydroxypropyl and hydroxybutyl acrylates and methacrylates. In addition to the above, other monomers are especially useful for ultra-violet light curable systems such as 2-acetoxyalkyl acrylates; pentaerythritol di-, tri- or tetra-acrylates and the like and may be added in any order.
The vinyl ester and copolymerizable vinyl monomer blend is a crosslinkable vinyl ester resin which is cured by mixing in a free radical forming catalyst in an amount ranging from 0.1 to about 5 percent by weight. Examples of these catalysts are benzoyl peroxide, t-butylhydroperoxide, methylethylketone peroxide and the like. It is frequently of value to add an accelerator such as N,N-dimethylaniline, cobalt naphthenate and the like.
The vinyl ester compositions of the present invention contain carbonate functionalities. These functionalities are those which were formed via transesterification reaction between the hydroxyl groups in the epoxy resin and carbonate groups in the polycarbonate or polycarbonate oligomer chains thus providing the precursor to the vinyl ester of the present invention. Reaction of this polycarbonate modified epoxy resin precursor with a monounsaturated monocarboxylic acid completes the synthesis of the compositions of the present invention. The polycarbonate modified vinyl ester resins when cured provide improved mechanical properties relative to their non-modified prior art counterparts.